Wireline logs were aquired at seven sites in the Newark Rift basin using dipmeter, gamma ray, resistivity, velocity, porosity, density, magnetic susceptibility, temperature, and acoustic telaviewer tools. The logs indicte that the formations are clay rich and dip on average 9° N-NW. Densities are relatively constrant (2.6-2.8 g/cc) and copressional velocities vary from 4.2-5.5 km/s. Thin uranium-rich layers and basalt flows are clearly deliniated. The boreholes are mostly in-gauge, but deviated, and borehole temperature gradients vary between 15 to 26° C/km. These data are potentially useful as indicators of fluid flow and regional stress, lithologic cycles, and for core orientation in the Newark Rift basin. back to bibliography

Virtually the entire Late Triassic and earliest Jurassic age section of the early Mesozoic Newark continental rift basin has been recovered in over 6770 m of continuous core as part of the Newark Basin Coring Project (NBCP). Core was collected using an offset drilling method at seven sites in the central part of the basin. The cores span most of the fluvial Stockton Formation, all of the lacustrine Lockatong and Passaic formations, the Orange Mountain Basalt, and nearly all of the lacustrine Feltville Formation. The cores allow for the first time the full Triassic-age part of the Newark basin stratigraphic sequence to be described in detail. This includes the gray, purple and red, mostly fluvial Stockton Formation as well as the 53 members that comprise the lacustrine Lockatong (mostly gray and black) and Passaic (mostly red) formations. The nearly 25% overlap zones between each of the stratigraphically adjacent cores are used to test lateral correlations in detail, scale the cores to one another, and combine them in a 4,660 m thick composite section. This composite shows that the entire post-Stockton sedimentary section consists of a hierarchy of sedimentary cycles, thought to be of Milankovitch climate cycle origin. Lithostratigraphic and magnetostratigraphic correlations between core overlap zones and outcrops demonstrates that the individual sedimentary cycles can be traced essentially basin wide. The agreement between the cyclostratigraphy and magnetostratigraphy shows both the cycles and the polarity boundaries to be isochronous horizons. Detailed analysis of the Newark basin shows that high-resolution cyclostratigraphy is possible in lacustrine, primarily red bed rift sequences and provides a fine-scale framework for global correlations and an understanding of continental tropical climate change.back to bibliography

Crowley et al. (1992, Science, 255: 705) propose that a roughly 10 Ky cycle, driven by climatic precession, should be present in long-term variations in precipitation over the continents at the equator. They point out that this frequency doubling of the precession cycle should amplify the effects of the roughly 100 Ky eccentricity cycle. Unfortunately, there are no Quaternary equatorial continental records that can be used to test this hypothesis, although several marine records have reported 10 Ky cyclicity. However, a Triassic venue can fill this, presumably temporary, continental desideratum because: 1) there are very long (>5 my), readily accessible rift basin lacustrine records spanning over 30¡ of paleolatitude and 30 my (~200-230 Ma); 2) these records can be correlated at very high levels of resolution because of recent advances in the Triassic magnetic polarity time scale; and 3) because of the extreme continentality of Pangean climate these lacustrine records should be extremely sensitive to insolation variations driven by celestial mechanics.

Here we report on a direct comparison of two contemporaneous, paleomagnetically correlated, cyclical lacustrine records from the Triassic Pangean tropics, both having formed in very large but isolated rift lakes. One is from the Dan River basin of VA and NC and was located at the paleoequator during the deposition of most of its preserved record. The other is from the Newark basin of NY, NJ, and PA and was deposited at about 3¡ N latitude during the interval represented in the Dan River section. The Newark basin record also spans the interval later in the Triassic during which the basin drifted to about 10¡ N. Paleomagnetic polarity correlation allows both sections to be placed in a common time scale. The direct comparison, using Fourier analysis, shows that 10 Ky cyclicity was dominant over 20 Ky in the Dan River section, while 20 Ky cycles dominated the Newark basin record over the same time interval. Strong cycles with prominent periods of about 100 and 400 Ky are present in both records, but there is little evidence of the 41 Ky cycle. The younger portion of the Newark basin record shows even less influence of the 10 Ky cycle. We attribute this 10 ky cyclicity at the Pangean equator to a doubling of the frequency of the cycle of climate precession, and infer that the 10 Ky cyclicity is a consequence of the two times per precession cycle that the solstice occurs at perihelion at the equator. It was during those times that convergence-driven precipitation was most intense and the rift lakes were deepest. We postulate that such a pattern has always been an attribute of continental equatorial climate.back to bibliography

During the Triassic, the Newark rift basin of Eastern North America was in the interior of tropical (3-7°N) Pangaea. Strikingly cyclical lacustrine rocks comprise most of the 6770 m of continuous core recovered from this basin by the Newark Basin Coring Project Six of the seven drill cores (each from 800-1300 m long) from this project are used here to construct a composite lake-level curve that provides a much needed record of long term variations in tropical climate. The main proxy of lake level and hence climate used to construct this lake level curve is a classification of water-depth related sedimentary structures and fabrics called depth ranks. We then use Fourier frequency analysis (both FFT and multitaper methods) and joint time-frequency approaches to resolve the periodic properties of the cyclicity and the secular drift in those properties. A consistent hierarchy in frequencies of the lake level cycle is present throughout the Triassic and earliest Jurassic portions of the cores. Calibration of the sediment accumulation rate by a variety of methods shows that these thickness periodicities are consistent with an origin in changes in precipitation governed by celestial mechanics. In specific, the full range of precession-related periods of lake level change are present, including the two peaks of the ~20,000 year cycle of climatic precession, the two peaks of the ~100,000 year eccentricity cycle, the single peak of the 412,900 year eccentricity cycle, and the ~2,000,000 year eccentricity cycle. There is good correspondence in the details of the joint-time frequency properties of cores and the astronomical predictions as well. In an ice-free world, the tropical climate of Pangaea responded strongly to astronomical forcing. Such precession-dominated forcing is still and probably always has been a prominent feature of tropical climate.back to bibliography